Method for surface grinding



Nov. 23, 1965 TAKASH; l ucH ETAL 3,218,763

METHOD FOR SURFACE GRINDING Filed Sept. 24, 1965 2 Sheets-Sheet 1 upward grind I downward gnnd Feed of Table INVENTOR. W M M BY United States Patent Office 3,218,763 Patented Nov. 23, 1965 3,218,763 METHOD FOR SURFACE GRINDING Takashi Kiknchi, Kawasaki, and Yasushi Mizuhara, Yokohama, Japan, assignors to Hitachi Limited, Tokyo, Japan, a corporation of Japan Filed Sept. 24, 1963, Ser. No. 311,187 2 Claims. (Cl. 51-281) The present invention relates to an improvement in automatic table operating system of a surface grinder.

The principal object of the invention is to provide an improved method of surface grinding by which perfectly plane ground surface can be obtained.

For a better understanding of the invention reference is taken to the accompanying drawings, in which:

FIG. 1 is a front elevation of a surface grinder embodying the invention;

FIG. 2 shows diagrams illustrating the relation between feed of table and depths of grind 1n upward and downward grindings;

FIG. 3 is an explanatory diagram showing a conventional table operating system of the surface grinder;

FIG. 4 is a sectional view for illustrating the profiles of surfaces ground by means of the grinding system in case of FIG. 3;

FIG. 5 shows diagrams illustrating the relation between the depth of grind and normal component of grinding resistance in upward and downward grindings;

FIG. 6 shows diagrams illustrating the relation between the depth from the grinding surface and the temperatures at different grinding depths;

FIG. 7 is an explanatory diagram illustrating the automatic table operating system of the present invention and FIG. 8 is a sectional view showing the profile of the surface ground according to the table operating system of the invention as shown in FIG. 7.

Referring to FIG. 1, the surface grinder shown is so constructed that a work piece 2 mounted on the table 1 is ground on the backward stroke as well as on the forward stroke of table by a rotary grinding wheel 3 rotating in the same rotational direction. As illustrated by FIG. 2, it is known that the amount of metal ground by upward grinding which feeds table in a direction opposite to the direction of wheel rotation is larger than that in the downward grinding which feeds table in the same direction as the wheel rotation.

In a conventional automatic table operating system of surface grinder, as shown in FIG. 3, the upward grinding is carried on while the table starts from the initial point a and advances in a direction of arrow along full line and reaches to the opposite end b, then the table is given a feed from end b to a position 0, the downward grinding is carried on while the table starts from the end c and reaches to the opposite end d, hereafter repeating the above mentioned operation until the table arrives at the last end e. The profile of the original surface to be ground as shown by dot-and-dash lines A-B in FIG. 4 has changed into profile as shown by full lines C-D, which are uneven in a plane normal to the travelling direction of table. Then the table is given a feed to move from the last end e to a position 1, thereafter the table is moved along the dotted line in the same direction as in the forward stroke, and when a grinding wheel arrives at the final end g the profile of ground surface is changed into profile as shown by the dotted line E-F in FIG. 4, which increases unevenness in the plane normal to the advancing direction of table, thus it is impossible to provide an exactly plane ground surface. Moreover, the grinding wheel causes wearing, tearing and falling off grains due to the grinding resistance which is different according to the actual grinding depths in the upward and downward grindings as shown in FIG. 5.

Furthermore, there is some temperature difference owing to the change of actual grinding depths in upward and downward grindings as shown in FIG. 6, resulting in uneven ground surface layer, so that it is impossible to provide a perfectly uniform layer all over the ground surface.

The above defects can be obviated by the invention and it provides an automatic table operating system, which is characterized in that the direction of the table motion in the forward stroke starting from one end h and arriving at the other end i as shown by the arrows along full line in FIG. 7 is made opposite to the direction of table movement in the backward stroke while the table starts from the end i and advances in the direction of the dotted line arrows and reaches the other end h.

With this arrangement, when the table started from one end 11 reaches the final end i, the profile of the ground surface is uneven in plane normal to the advancing direction of table as shown by the full line C-D in FIG. 8, yet when the table started from the final end i returns to the starting end h, the profile of the ground surface is made smooth, accurate, and free from uneveness as shown by the dotted line G-H in FIG. 8.

What We claim is:

1. The method of grinding a planar surface on a workpiece with a rotatably driven grinding wheel which comprises bringing the grinding wheel into engagement with said workpiece, moving the workpiece under said wheel in a first forward stroke, indexing the work at the end of said first forward stroke to displace the wheel in a direction transverse to said first forward stroke, moving the work under said grinding wheel in a first return stroke opposite in direction to and parallel to said first forward stroke, at the end of said return stroke reversing the direction of movement of said workpiece to move the workpiece with respect to the grinding wheel in a second forward stroke coincident with the path of said first return stroke, indexing the work to locate the grinding wheel in the same position with respect to said workpiece as occupied by said wheel at the end of said first forward stroke, and moving said workpiece in a second return stroke coinciding with the path of and opposite to the direction of said first forward stroke to grind the surface of said workpiece to a flat planar surface.

2. The method of grinding a planar surface on a workpiece with a rotatably driven grinding wheel which comprises placing said wheel in grinding engagement with the surface of said workpiece at an initial point of grinding, moving said workpiece under said grinding wheel in a plurality of forward strokes and return strokes, each of said forward strokes being followed by a return stroke along a parallel path displaced from said forward stroke, and then reversing the direction of movement of said workpiece under said grinding wheel to retrace the paths of said forward and return strokes with said workpiece being moved in the opposite direction to that of the original movement in each of said strokes, to provide a planar surface when said grinding wheel reaches said initial point of grinding of said workpiece.

References Cited by the Examiner UNITED STATES PATENTS 1,978,181 10/1934 Whittles 51-92 2,080,976 5/1937 Wood 5192 2,127,877 8/1938 Maglott 5 l--92 LESTER M. SWINGLE, Primary Examiner. 

2. THE METHOD OF GRINDING A PLANAR SURFACE ON A WORKPIECE WITH A ROTATABLY DRIVEN GRINDING WHEEL WHICH COMPRISES PLACING SAID WHEEL IN GRINDING ENGAGEMENT WITH THE SURFACE OF SAID WORKPIECE AT AN INITIAL POINT OF GRINDING, MOVING SAID WORKPIECE UNDER SAID GRINDING WHEEL IN A PLURALITY OF FORWARD STROKES AND RETURN STROKES, EACH OF SAID FORWARD STROKES BEING FOLLOWED BY A RETURN STROKE ALONG A PARALLEL PATH DISPLACED FROM SAID FORWARD STROKE, AND THEN REVERSING THE DIRECTION OF MOVEMENT OF SAID WORKPIECE UNDER SAID GRINDING WHEEL TO RETRACE THE PATHS 